MODELING OF THE STRENGTH'S LOSS AND VOID APPEARANCE IN THE UNDERGROUND STRUCTURES OF PARIS METRO MODELISATION DE LA PERTE DE RESISTANCE ET DE L'APPARITION DES VIDES DANS LES OUVRAGES SOUTERRAINS DU METRO PARISIEN

Several tests as drilling, impedance or georadar, were performed in order to know the current state of Paris Metro galleries and tunnels. The tunnel linings of these underground structures appear slightly fragmented and very fragmented in the extrados of the abutments. The aim of our study is to propose a numerical model which can represent the tunnel's behavior over its life. The main aspects taken into account in this model are the loss of strength due to different alteration processes and creation of voids which are caused by the timbering rot and disaggregation of ancient masonry. Viscoplastic with strain softening model is used to reproduce localization of the deformation associated to crack appearance. The numerical results show that we can reproduce the underground structure's behavior during degradation and assess the state of different structure components. Several simulations were conducted, and the robustness of the numerical model gauged, which allows us to confirm that this approach is applicable to this kind of construction and / or other structures designed by this type of building materials and undergo the same weathering process.